Debugging in JRuby 9.2.x

1. Add these gems in gemfile or gemspec:

gem 'ruby-debug'
gem 'columnize'

2. Add require 'ruby-debug' in your project.
3. Add breakpoints with debugger keyword.
4. Run jruby with --debug flag:

jruby --debug -S bundle exec <command>

Create ~/.rdebugrc

Unlike pry or byebug where we can simply call the variable to see its value, we have to use p to print the value. For example, my_var vs p my_var. We can change this behavior to autoeval by adding the following lines to a ~/.rdebugrc file:

set autolist
set autoeval
set autoreload

SimpleCov

SimpleCov does not work with ruby-debug. Temporarily uncomment it from your MRI based while it runs on JRuby. See ruby-debug/ruby-debug#27 for more information.

Sources

https://github.com/jruby/jruby/wiki/UsingTheJRubyDebugger https://gist.github.com/klappradla/69029a982ade44e20e124c29b1c00541